Vehicle suspensions generally assist in maintaining ride conditions that are acceptable to vehicle passengers. In particular, suspensions isolate the vehicle passengers from large vertical accelerations including those caused by bumps and other road disturbances.
Know vehicle suspensions generally include shock absorbers, springs, housing components, and various connecting components. Modern vehicle suspensions, such as semi-active or active suspensions, further include a control system wherein various sensors located throughout the vehicle measure motion of vehicle components including wheel motion and wherein a controller utilizes the motion measurements to control the action of suspension components. In one type of semi-active suspension, the controller sends signals changing damping levels of hydraulic shock absorbers of the suspension in response to signals from sensors located proximate each wheel.
When a wheel begins to vibrate at a frequency near a natural resonance frequency of the suspension—known as a wheel hop frequency—the vibrations are amplified. One type of suspension system has a single damping strategy for both low frequency vibrations and high frequency vibrations. The single strategy provides some damping level to the suspension under both high and low frequency conditions. However, neither damping level is specifically tuned to control vibrations in a specific frequency range.
Another type of suspension system has a controller that controls a condition where a chatter bump frequency (that is, the frequency of relative vertical movement between sprung and unsprung vehicle components in response to bumps of the road surface) is close to the vehicle's wheel hop frequency. These systems detect the situations in which the chatter bump frequency is close to the wheel hop frequency by using filters such as bandpass filters or a combination of low and high pass filters. However, systems having bandpass or low and high pass filters assume a preprogrammed wheel hop frequency and, therefore, do not automatically adapt to changes in the vehicle such as vehicle customizations and changes in vehicle component properties over time.